10. Dwarf galaxies and stellar formation

Dwarf galaxies that lived about 9 to 10 billion years ago had bursts of star formation, which implies that many, if not most, of the stars in such galaxies in the present-day universe form in the same way. This image shows 18 of the 69 galaxies studied.

8. Base of black hole's jet spied

7. DIY funding ramps up

Privately funded astronomical instruments are becoming more popular, the way observatories used to be financed. In 2012, the organization behind the Giant Magellan Telescope announced it wouldn't apply for NSF funding, the Discovery Channel Telescope saw first light without any state or federal assistance, and the B612 Foundation revealed its plans to develop a privately funded space telescope.

4. Exoplanets discovered in surprising situations

Scientists uncovered new worlds that orbit binary stars (as seen in the illustration), ones that orbit suns lacking expected heavier elements, ones that survived their star's red-giant phase, and even a world orbiting a sun in the star system nearest to ours.

3. Commercial craft takes historic flights

SpaceX's Dragon capsule made history as the first privately developed craft to berth with the International Space Station in May. The company launched its first of many regular supply runs to the station five months later.

2. Astronomers question how stars blow up

A type Ia supernova can result from two different paths, and more discoveries in 2012 questioned whether the energy emitted during the explosion is consistent. The concern has big consequences: Such supernova measurements have been used to measure the universe's accelerating expansion.